Botrydium

Botrydium:-

1. Classification:-

Division:- Xanthophyta

Class:- Xanthophyceae

Order:- Heterosiphonales

Family:- Botrydiaceae

Genus:- Botrydium

2. Habit and Habitat:-

> Botrydium is a very common epipelic alga living on humid mud of lakes and pond shores, where it can produce very large clusters.

> Its single-celled, multinucleate vesicles are attached to the substratum by a sort of rhizoid apparatus entering the mud.

> Botrychium frequently grows intermingled with a green alga Protosiphon to which it bears a superfecial resemblance.

> Important species:-

i. B. granulatum

ii. B. tuberosum

iii. B. wallrothii

iv. B. divisum

3. Thallus structure:-

> The thallus is unicellular and is differentiated into an upper sub-aerial part and a branched rhizoidal part, which penetrates the soil.

> The sub-aerial part is globose, pear-shaped or elongated, cylindrical in form, depending on the environmental conditions, and about 1 -2 mm. in diameter. It is surrounded by a tough wall, within which is a peripheral layer of protoplasm surrounding a central vacuole.

> The protoplasm contains many nuclei and discoid chromatophores with pyrenoid-like bodies, but oil instead of starch is formed as food-reserve.

> The rhizoidal portion shows various degrees of branching and is colourless due to the absence of chloroplast.

> Numerous nuclei are found distributed in the vacuolated cytoplasm.

> It is evident that within the body of the unicellular alga the protoplasm is continuous throughout, and is characteristic of a coenocyte.

4. Reproduction:- Botrydium usually reproduces asexually, but sexual reproduction has also been reported in some cases. It is incapable of any vegetative reproduction.

a. Asexual reproduction:- It takes place by means of zoospores, aplanospores or hypnospores.

i. Zoospores:-

> When the plants are flooded with water, zoospores ate produced.

> The protoplasm of the vesicular portion of the plant body, by repeated divisions, forms numerous uninucleate masses which are ultimately metamorphozed into pear-shaped zoospores.

> Each zoospores possesses anteriorly two flagella of unequal lengths.

> Due to the gelatinization of the apical portion of the vesicle an opening is formed, through which the zoospores escape and these finally develop into new plants.

ii. Aplanospores:-

> When the plants grow in a comparatively dry soil, they form aplanospores.

> The formation of aplanospores is similar to that of zoospores, but the ultimate protoplasmic masses are either uninucleate or multinucleate, which become rounded and develop a wall around each.

> Aplanospores, under favourable conditions, germinate directly into new plants.

iii. Hypnospores:-

> Thick-walled uninucleate or multinucleate hypnospores may also be formed from the aplanospores of the vesicular portion.

> Uninucleate hypnospore germinates and directly forms a new thallus.

> Multinucleate hypnospores, on the other hand, at the time of germination forms a number of zoospores or aplanospores, each of which after liberation forms a new plant.

iv. Resting bodies:- They are formed under dry conditions. 4 types of resting bodies are formed:

i. Macrocyst

ii. Sporocyst

iii. Rhizocyst:- In some cases, the protoplasm migrates into the rhizoidal portion and becomes separated into a number of multinucleate, serially-arranged segments, each of which eventually becomes surrounded by a thick wall. Eg.- B. granulatum

iv. Tubers:- The protoplasm of the aerial vesicle migrates into the rhizoidal portion. There it collects at the tips of the rhizoids to form tubers. Eg.- B. tuberosum